<script id="draw-shader-vs" type="x-shader/x-vertex">
precision highp float;

attribute vec3 inPos;
attribute vec3 inNV;

varying vec4 v_clip_pos;

uniform mat4 u_projectionMat44;
uniform mat4 u_viewMat44;
uniform mat4 u_modelMat44;

void main()
{   
    vec4 pos  = u_viewMat44 * u_modelMat44 * vec4( inPos, 1.0 );

    v_clip_pos  = u_projectionMat44 * pos;
    gl_Position = v_clip_pos;
}
</script>
  
<script id="draw-shader-fs" type="x-shader/x-fragment">
#extension GL_OES_standard_derivatives : enable
precision mediump float;

varying vec4 v_clip_pos;

uniform highp vec3 color;

void main()
{
    vec3  ndc_pos = v_clip_pos.xyz / v_clip_pos.w;
    vec3  dx      = dFdx( ndc_pos );
    vec3  dy      = dFdy( ndc_pos );

    vec3 N = normalize(cross(dx, dy));
    N *= sign(N.z);
    vec3 L = vec3(0.0, 0.0, 1.0); 
    float NdotL = dot(N, L); 

    vec3 diffuse_color = color * NdotL;
    gl_FragColor       = vec4( diffuse_color.rgb, 1.0 );
} 
</script>

<style>
html,body { margin: 0; overflow: hidden; }
#gui { position : absolute; top : 0; left : 0; font-size : large; }
#ref-link { position : absolute; bottom : 0; left : 0; font-size : large; }  
</style>

<body>
    
<canvas id="canvas" style="border: none;"></canvas>


<div id="ref-link">
<a href="https://stackoverflow.com/questions/50921461/3d-object-is-colored-in-a-way-that-looks-like-a-2d-object/50931560#50931560">
<font color= #CCF>3D object is colored in a way that looks like a 2D object</font> 
</a><br/>
<a href="https://stackoverflow.com/questions/53443845/ambient-lighting-with-opengl-glsl">
<font color= #CCF>Diffuse light with OpenGL GLSL</font> 
</a>
</div>

</body>

<script type="text/javascript">

(function loadscene() {

var gl, progDraw, vp_size;
var bufCube = {};

function render(delteMS){

    Camera.create();
    Camera.vp = vp_size;
        
    gl.viewport( 0, 0, vp_size[0], vp_size[1] );
    gl.enable( gl.DEPTH_TEST );
    gl.clearColor( 0.0, 0.0, 0.0, 1.0 );
    gl.clear( gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT );

    // set up draw shader
    ShProg.Use( progDraw );
    ShProg.SetM44( progDraw, "u_projectionMat44", Camera.Perspective() );
    ShProg.SetM44( progDraw, "u_viewMat44", Camera.LookAt() );
    var modelMat = IdentM44()
    modelMat = RotateAxis( modelMat, CalcAng( delteMS, 13.0 ), 0 );
    modelMat = RotateAxis( modelMat, CalcAng( delteMS, 17.0 ), 1 );
    ShProg.SetM44( progDraw, "u_modelMat44", modelMat );
    ShProg.SetF3( progDraw, "color", [0.9, 0.9, 0.5] );
    
    // draw scene
    VertexBuffer.Draw( bufCube );

    requestAnimationFrame(render);
}

function resize() {
    //vp_size = [gl.drawingBufferWidth, gl.drawingBufferHeight];
    vp_size = [window.innerWidth, window.innerHeight];
    //vp_size = [256, 256]
    canvas.width = vp_size[0];
    canvas.height = vp_size[1];
}

function initScene() {

    canvas = document.getElementById( "canvas");
    gl = canvas.getContext( "experimental-webgl" );
    if ( !gl )
    return null;
    var ext_standard_derivatives = gl.getExtension( "OES_standard_derivatives" );  // dFdx, dFdy
    if (!ext_standard_derivatives)
        alert('no standard derivatives support (no dFdx, dFdy)');
    
    progDraw = ShProg.Create( 
    [ { source : "draw-shader-vs", stage : gl.VERTEX_SHADER },
        { source : "draw-shader-fs", stage : gl.FRAGMENT_SHADER }
    ] );
    if ( !progDraw.progObj )
        return null;
    progDraw.inPos = ShProg.AttrI( progDraw, "inPos" );
    progDraw.inNV  = ShProg.AttrI( progDraw, "inNV" );
    // create sphere
    var layer_size = 16, circum_size = 32;
    var rad_circum = 1.0;
    var rad_tube = 0.5;
    var sphere_pts = [];
    var sphere_nv = [];
    sphere_pts.push( 0.0, 0.0, -rad_circum );
    sphere_nv.push( 0.0, 0.0, -1.0 );
    for ( var i_l = 1; i_l < layer_size; ++ i_l ) {
        var angH = (1.0 - i_l / layer_size) * Math.PI;
        var h = Math.cos( angH );
        var r = Math.sin( angH );
        for ( var i_c = 0; i_c < circum_size; ++ i_c ) {
            var circumX = Math.cos(2 * Math.PI * i_c / circum_size);
            var circumY = Math.sin(2 * Math.PI * i_c / circum_size);
            sphere_pts.push( r * circumX * rad_circum, r * circumY * rad_circum, h * rad_circum );
            sphere_nv.push( r * circumX, r * circumY, h );
        }
    }
    sphere_pts.push( 0.0, 0.0, rad_circum );
    sphere_nv.push( 0.0, 0.0, 1.0 );
    var sphere_inx = [];
    for ( var i_c = 0; i_c < circum_size; ++ i_c ) {
        sphere_inx.push( i_c+1, 0, (i_c+1) % circum_size + 1 )
    }
    for ( var i_l = 0; i_l < layer_size-2; ++ i_l ) {
        var l1 = i_l * circum_size + 1;
        var l2 = (i_l+1) * circum_size + 1
        for ( var i_c = 0; i_c < circum_size; ++ i_c ) {
            var i_n = (i_c+1) % circum_size;
            sphere_inx.push( l1+i_c, l1+i_n, l2+i_c, l1+i_n, l2+i_n, l2+i_c );
        }
    }
    for ( var i_c = 0; i_c < circum_size; ++ i_c ) {
        var i_start = 1 + (layer_size-2) * circum_size;
        var i_n = (i_c+1) % circum_size;
        sphere_inx.push( i_start + i_c, i_start + i_n, sphere_pts.length/3-1 );
    }
    bufCube = VertexBuffer.Create(
    [ { data : sphere_pts, attrSize : 3, attrLoc : progDraw.inPos },
    { data : sphere_nv,  attrSize : 3, attrLoc : progDraw.inNV } ],
    sphere_inx );
    
    window.onresize = resize;
    resize();
    requestAnimationFrame(render);
}

function Fract( val ) { 
    return val - Math.trunc( val );
}
function CalcAng( deltaTime, intervall ) {
    return Fract( deltaTime / (1000*intervall) ) * 2.0 * Math.PI;
}
function CalcMove( deltaTime, intervall, range ) {
    var pos = self.Fract( deltaTime / (1000*intervall) ) * 2.0
    var pos = pos < 1.0 ? pos : (2.0-pos)
    return range[0] + (range[1] - range[0]) * pos;
}    
function EllipticalPosition( a, b, angRag ) {
    var a_b = a * a - b * b
    var ea = (a_b <= 0) ? 0 : Math.sqrt( a_b );
    var eb = (a_b >= 0) ? 0 : Math.sqrt( -a_b );
    return [ a * Math.sin( angRag ) - ea, b * Math.cos( angRag ) - eb, 0 ];
}

glArrayType = typeof Float32Array !="undefined" ? Float32Array : ( typeof WebGLFloatArray != "undefined" ? WebGLFloatArray : Array );

function IdentM44() {
var m = new glArrayType(16);
m[0]  = 1; m[1]  = 0; m[2]  = 0; m[3]  = 0;
m[4]  = 0; m[5]  = 1; m[6]  = 0; m[7]  = 0;
m[8]  = 0; m[9]  = 0; m[10] = 1; m[11] = 0;
m[12] = 0; m[13] = 0; m[14] = 0; m[15] = 1;
return m;
};

function RotateAxis(matA, angRad, axis) {
    var aMap = [ [1, 2], [2, 0], [0, 1] ];
    var a0 = aMap[axis][0], a1 = aMap[axis][1]; 
    var sinAng = Math.sin(angRad), cosAng = Math.cos(angRad);
    var matB = new glArrayType(16);
    for ( var i = 0; i < 16; ++ i ) matB[i] = matA[i];
    for ( var i = 0; i < 3; ++ i ) {
        matB[a0*4+i] = matA[a0*4+i] * cosAng + matA[a1*4+i] * sinAng;
        matB[a1*4+i] = matA[a0*4+i] * -sinAng + matA[a1*4+i] * cosAng;
    }
    return matB;
}

function Cross( a, b ) { return [ a[1] * b[2] - a[2] * b[1], a[2] * b[0] - a[0] * b[2], a[0] * b[1] - a[1] * b[0], 0.0 ]; }
function Dot( a, b ) { return a[0]*b[0] + a[1]*b[1] + a[2]*b[2]; }
function Normalize( v ) {
    var len = Math.sqrt( v[0] * v[0] + v[1] * v[1] + v[2] * v[2] );
    return [ v[0] / len, v[1] / len, v[2] / len ];
}

var Camera = {};
Camera.create = function() {
    this.pos    = [0, 1.5, 0.0];
    this.target = [0, 0, 0];
    this.up     = [0, 0, 1];
    this.fov_y  = 90;
    this.vp     = [800, 600];
    this.near   = 0.5;
    this.far    = 100.0;
}
Camera.Perspective = function() {
    var fn = this.far + this.near;
    var f_n = this.far - this.near;
    var r = this.vp[0] / this.vp[1];
    var t = 1 / Math.tan( Math.PI * this.fov_y / 360 );
    var m = IdentM44();
    m[0]  = t/r; m[1]  = 0; m[2]  =  0;                              m[3]  = 0;
    m[4]  = 0;   m[5]  = t; m[6]  =  0;                              m[7]  = 0;
    m[8]  = 0;   m[9]  = 0; m[10] = -fn / f_n;                       m[11] = -1;
    m[12] = 0;   m[13] = 0; m[14] = -2 * this.far * this.near / f_n; m[15] =  0;
    return m;
}
Camera.LookAt = function() {
    var mz = Normalize( [ this.pos[0]-this.target[0], this.pos[1]-this.target[1], this.pos[2]-this.target[2] ] );
    var mx = Normalize( Cross( this.up, mz ) );
    var my = Normalize( Cross( mz, mx ) );
    var tx = Dot( mx, this.pos );
    var ty = Dot( my, this.pos );
    var tz = Dot( [-mz[0], -mz[1], -mz[2]], this.pos ); 
    var m = IdentM44();
    m[0]  = mx[0]; m[1]  = my[0]; m[2]  = mz[0]; m[3]  = 0;
    m[4]  = mx[1]; m[5]  = my[1]; m[6]  = mz[1]; m[7]  = 0;
    m[8]  = mx[2]; m[9]  = my[2]; m[10] = mz[2]; m[11] = 0;
    m[12] = tx;    m[13] = ty;    m[14] = tz;    m[15] = 1; 
    return m;
} 

var ShProg = {
Create: function (shaderList) {
    var shaderObjs = [];
    for (var i_sh = 0; i_sh < shaderList.length; ++i_sh) {
        var shderObj = this.Compile(shaderList[i_sh].source, shaderList[i_sh].stage);
        if (shderObj) shaderObjs.push(shderObj);
    }
    var prog = {}
    prog.progObj = this.Link(shaderObjs)
    if (prog.progObj) {
        prog.attrInx = {};
        var noOfAttributes = gl.getProgramParameter(prog.progObj, gl.ACTIVE_ATTRIBUTES);
        for (var i_n = 0; i_n < noOfAttributes; ++i_n) {
            var name = gl.getActiveAttrib(prog.progObj, i_n).name;
            prog.attrInx[name] = gl.getAttribLocation(prog.progObj, name);
        }
        prog.uniLoc = {};
        var noOfUniforms = gl.getProgramParameter(prog.progObj, gl.ACTIVE_UNIFORMS);
        for (var i_n = 0; i_n < noOfUniforms; ++i_n) {
            var name = gl.getActiveUniform(prog.progObj, i_n).name;
            prog.uniLoc[name] = gl.getUniformLocation(prog.progObj, name);
        }
    }
    return prog;
},
AttrI: function (prog, name) { return prog.attrInx[name]; },
UniformL: function (prog, name) { return prog.uniLoc[name]; },
Use: function (prog) { gl.useProgram(prog.progObj); },
SetI1: function (prog, name, val) { if (prog.uniLoc[name]) gl.uniform1i(prog.uniLoc[name], val); },
SetF1: function (prog, name, val) { if (prog.uniLoc[name]) gl.uniform1f(prog.uniLoc[name], val); },
SetF2: function (prog, name, arr) { if (prog.uniLoc[name]) gl.uniform2fv(prog.uniLoc[name], arr); },
SetF3: function (prog, name, arr) { if (prog.uniLoc[name]) gl.uniform3fv(prog.uniLoc[name], arr); },
SetF4: function (prog, name, arr) { if (prog.uniLoc[name]) gl.uniform4fv(prog.uniLoc[name], arr); },
SetM33: function (prog, name, mat) { if (prog.uniLoc[name]) gl.uniformMatrix3fv(prog.uniLoc[name], false, mat); },
SetM44: function (prog, name, mat) { if (prog.uniLoc[name]) gl.uniformMatrix4fv(prog.uniLoc[name], false, mat); },
Compile: function (source, shaderStage) {
    var shaderScript = document.getElementById(source);
    if (shaderScript)
        source = shaderScript.text;
    var shaderObj = gl.createShader(shaderStage);
    gl.shaderSource(shaderObj, source);
    gl.compileShader(shaderObj);
    var status = gl.getShaderParameter(shaderObj, gl.COMPILE_STATUS);
    if (!status) alert(gl.getShaderInfoLog(shaderObj));
    return status ? shaderObj : null;
},
Link: function (shaderObjs) {
    var prog = gl.createProgram();
    for (var i_sh = 0; i_sh < shaderObjs.length; ++i_sh)
        gl.attachShader(prog, shaderObjs[i_sh]);
    gl.linkProgram(prog);
    status = gl.getProgramParameter(prog, gl.LINK_STATUS);
    if ( !status ) alert(gl.getProgramInfoLog(prog));
    return status ? prog : null;
} };

var VertexBuffer = {
Create: function(attribs, indices, type) {
    var buffer = { buf: [], attr: [], inx: gl.createBuffer(), inxLen: indices.length, primitive_type: type ? type : gl.TRIANGLES };
    for (var i=0; i<attribs.length; ++i) {
        buffer.buf.push(gl.createBuffer());
        buffer.attr.push({ size : attribs[i].attrSize, loc : attribs[i].attrLoc, no_of: attribs[i].data.length/attribs[i].attrSize });
        gl.bindBuffer(gl.ARRAY_BUFFER, buffer.buf[i]);
        gl.bufferData(gl.ARRAY_BUFFER, new Float32Array( attribs[i].data ), gl.STATIC_DRAW);
    }
    gl.bindBuffer(gl.ARRAY_BUFFER, null);
    if ( buffer.inxLen > 0 ) {
        gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, buffer.inx);
        gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, new Uint16Array( indices ), gl.STATIC_DRAW);
        gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, null);
    }
    return buffer;
},
Draw: function(bufObj) {
    for (var i=0; i<bufObj.buf.length; ++i) {
        gl.bindBuffer(gl.ARRAY_BUFFER, bufObj.buf[i]);
        gl.vertexAttribPointer(bufObj.attr[i].loc, bufObj.attr[i].size, gl.FLOAT, false, 0, 0);
        gl.enableVertexAttribArray( bufObj.attr[i].loc);
    }
    if ( bufObj.inxLen > 0 ) {
        gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, bufObj.inx);
        gl.drawElements(bufObj.primitive_type, bufObj.inxLen, gl.UNSIGNED_SHORT, 0);
        gl.bindBuffer( gl.ELEMENT_ARRAY_BUFFER, null );
    }
    else
        gl.drawArrays(bufObj.primitive_type, 0, bufObj.attr[0].no_of );
    for (var i=0; i<bufObj.buf.length; ++i)
        gl.disableVertexAttribArray(bufObj.attr[i].loc);
    gl.bindBuffer( gl.ARRAY_BUFFER, null );
} };

initScene();

})();
</script>